In my U.S. Pat. No. 3,469,582 I have provided a surgical suction control unit employing a diaphragm which opens the flow passage by the simple procedure of covering a control hole, e.g. by use of the index finger of the person holding the unit. In this construction a vacuum bleed through a small passage maintains a vacuum level over the diaphragm, and holds the diaphragm in open position, when the finger closes the hole. However when the finger is removed from the control hole to allow ambient pressure to enter the control chamber, the higher pressure condition forces the diaphragm to close the flow passage.
This control unit has been effective in surgical suction devices and other applications, but, in the constructions as taught in my prior patent and as made in production, significant problems have remained.
One of the difficulties concerns the provision of an accurately sized vacuum bleed passage for connection of the control chamber to the vacuum source. If this passage is too large it wastes vacuum and the flow is noisy. If on the other hand this passage is too small, insufficient vacuum level is acquired in the control chamber and the unit does not function properly. In production, expensive molding dies having accurately fitted molding pins have been required to form such passages.
Another difficulty concerns the fact that fluids being sucked through the device often contain substances which tend to clog the vacuum bleed passage. Because of the wish to have the passage self-cleaning, the preferred form of the invention has been a tiny hole molded into the thin diaphragm, as shown in FIGS. 12-15 of my prior patent. It has however been particularly difficult to size accurately this passage through the diaphragm.
In the preferred embodiments of the past, the diaphragm, held by its periphery in the position as shown in FIGS. 12-15 of my prior patent, has been thin and flexible in order to achieve the proper flexing motion. Such a diaphragm has the disadvantage of making loud noise under certain flow conditions, for instance during partial clogging of the vacuum bleed passage or partial occlusion of the finger control port. The noise has been very high pitch, making the unit objectionable.
Still other problems have concerned the time and expense of manufacture of the unit. In present commercial forms the parts must be clamped in a jig and the elements are then cemented together.
Purposes of the present invention are to overcome these disadvantages and to provide an improved suction control unit.